The present disclosure relates to an electrode pad structure for semiconductor devices.
In recent years, there is a demand for a reduction in height of a chip including a wiring layer of a CCD (charge coupled device) or an imaging sensor in view of a relationship between the height and an optical characteristic thereof, in addition to improvements in function and scale of integration of a semiconductor device. Therefore, it is necessary to reduce the thickness of the wiring layer as well in the future. Wirings may be made of Cu in a state-of-the-art process. In this case, a Cu film is formed by plating before removal by Chemical Mechanical Polishing (CMP).
FIG. 7 is a cross-sectional view of a conventional semiconductor device having an electrode pad structure disclosed in Japanese Unexamined Patent Application Publication No. 2007-123546. As shown in FIG. 7, a first insulating film 102 is formed on a semiconductor substrate 101, and a second insulating film 103 and a first layer Cu wiring 104 are formed on the first insulating film 102. A third insulating film 105, and Cu connection vias 106 contacting the first layer Cu wiring 104 are formed on the second insulating film 103 and the first layer Cu wiring 104. A fourth insulating film 107, and a second layer Cu wiring 108 contacting the Cu connection vias 106 are formed on the third insulating film 105 and the Cu connection vias 106. A fifth insulating film 109, and Cu connection vias 110 contacting the second layer Cu wiring 108 are formed on the fourth insulating film 107 and the second layer Cu wiring 108. A sixth insulating film 111, and an uppermost layer Cu pad 112 contacting the Cu connection vias 110 are formed on the fifth insulating film 109 and the Cu connection vias 110. A passivation film 113 is formed on the sixth insulating film 111 and the uppermost layer Cu pad 112. An opening 114 through which a center portion of the uppermost layer Cu pad 112 is exposed is formed in the passivation film 113. An Al pad 116 is formed on the uppermost layer Cu pad 112 exposed in the opening 114 and the passivation film 113 around the opening 114 with a barrier film 115 being interposed therebetween. A tip of a bonding wire (not shown) is connected to the Al pad 116.